CHIP: A link between the chaperone and proteasome system

描述（由申请人提供）：70和90 kda热休克蛋白（Hsps）以其作为分子伴侣的作用而闻名，参与新生蛋白的折叠、成熟和适当的亚细胞靶向，或者相反，参与被细胞应激源错误折叠或以其他方式损坏的蛋白质的功能恢复。然而，热休克蛋白参与多种过程-细胞内信号事件，增殖，分化和蛋白质的靶向降解-似乎与蛋白质折叠只是间接相关，或者根本不相关。与此同时，越来越明显的是，分子伴侣并不代表细胞应激反应的总和，除了蛋白质重折叠之外，还需要一系列事件来维持生存能力，并在不利情况下保护细胞内环境。我们于1999年在应激反应基因筛选中发现了CHIP （hsc70相互作用蛋白的羧基末端）。此后，我们发现CHIP与伴侣蛋白Hsc70、Hsp70和Hsp90相互作用，并对其功能产生复杂而协调的影响。此外，CHIP具有泛素连接酶活性，在细胞质内调节蛋白质质量控制中起关键作用。最后，我们通过体外和体内实验发现，CHIP是细胞和机体应激反应的中心调节因子。令人惊讶的是，至少其中一些作用似乎与CHIP对转录、信号传导和代谢反应的特定作用有关。这项拨款的目的是作为我们最初筛选参与分子伴侣事件的蛋白质的逻辑延伸。为了实现我们的目标，我们制定了一种新颖且高度集成的方法，使用体外和体内检测。本建议的目的是：(1)。使用组合转录组/蛋白质组分析检查CHIP对细胞应激背景下mRNA和蛋白质表达全局变化的影响；(2)表征CHIP在细胞信号传导和代谢反应中的作用；(3)评估CHIP在体内病理生理应激中的综合作用。本提案的范围旨在利用最先进的分子生物学技术解决相关的生物学和生理学问题。从该提案中获得的知识应该提供关于这些不同途径如何调节受泛素/蛋白酶体系统控制的生理和病理过程的关键信息，并可能为治疗涉及该系统的疾病提供潜在的治疗靶点。

DESCRIPTION (provided by applicant): 70- and 90-kDa heat shock proteins (Hsps) are best known by their roles as molecular chaperones, participating in the folding, maturation, and proper subcellular targeting of nascent proteins or, conversely, the recovery of function of proteins that have been misfolded or otherwise damaged by cellular stressors. However, Hsps participate in a variety of processes- intracellular signaling events, proliferation, differentiation, and targeted degradation of proteins- that seem related to protein folding only indirectly, or not at all. At the same time, it is becoming increasingly apparent that molecular chaperones do not represent the sum total of the cell stress response, and that a range of events other than protein refolding are required to maintain viability and protect the intracellular environment in adverse circumstances. We identified CHIP (carboxyl-terminus of Hsc70-interacting protein) in a screen for stress-responsive genes in 1999. Since then, we have found that CHIP interacts with the chaperones Hsc70, Hsp70, and Hsp90 and has complex and coordinated effects on their functions. In addition, CHIP has ubiquitin ligase activity and plays a critical role in regulating protein quality control within the cytoplasm. Finally, we have found using both in vitro and in vivo approaches that CHIP is a central regulator of cellular and organismal stress responses. Surprisingly, at least some of these effects seem to be related to specific effects of CHIP on transcriptional, signaling, and metabolic responses. The aims of this grant are intended as a logical extension of our initial screen for proteins participating in molecular chaperone events. To accomplish our aims, we have formulated a novel and highly integrated approach using both in vitro and in vivo assays. The aims of this proposal are to: (1). Examine the consequences of CHIP on global changes in mRNA and protein expression in the context of cellular stress using a combined transcriptome/proteome analysis; (2) Characterize the role of CHIP on cell signaling and metabolic responses and (3) Evaluate the integrated effects of CHIP on pathophysiologic stress in vivo. The scope of this proposal is intended to address relevant biological and physiological questions using state of the art molecular biology techniques. Knowledge gained from this proposal should provide crucial information about how these various pathways regulate physiologic and pathologic processes that are under control of the ubiquitin/proteasome system and may provide potential therapeutic targets for treatment of diseases where this system is involved. PUBLIC HEALTH RELEVANCE: Proper protein folding is essential for optimum protein performance and normal cellular function. During synthesis of new proteins and refolding of denatured proteins, cooperation between the cell's molecular chaperones and its degradation machinery must occur because some proteins cannot attain their correct tertiary conformation spontaneously. The mutually exclusive pathways of folding and degradation constitute the cell's protein quality control system. The chaperone and ubiquitin-proteasome systems play critical roles in regulating stress-responsive signaling and cellular protective mechanisms in health and disease. Our overall goal is to determine how the molecular and physiologic functions of CHIP, a molecular chaperone, are coordinated to orchestrate its stress response capabilities. These studies will help us develop new models about the relationship between cytoplasmic quality control mechanisms and the cellular stress response.